A method of observing a small child in a vehicle is performed by mounting a novel mirror assembly to a portion of the vehicle. The gear train reduction includes an input stage and a planetary gear drive output stage that includes a first portion of the reversing mechanism. The path is validated if the bit error rate is within a predefined range. The housing includes a through cavity adapted to hold a viewing instrument, such as a cystoscope to allow accurate positioning of the injector. Each of the plurality of operating condition states includes a substantially fixed switch on time. The transducers are configured to generate and receive first and second acoustic waves in the tubular.